About one fifth of Koreans are going crazy trying to get as many hearts as possible every day to play mobile game Anipang. That's because players need one heart for a round of the simple but addictive one-minute game.

Anipang has become an obsession for Koreans of all ages. You can easily spot commuters who are possessed by the game.

The name _ a compound of "ani" from animal and "pang" from the onomatopoeic Korean word meaning explosion _ has lured more than half of all smartphone users and positioned itself as a must-have app here.

According to producer, Sundaytoz, the game has been downloaded more than 20 million times in total and about 10 million people are playing it daily. It means that nearly 70 percent of smartphone users have the app on their handsets.

It can be downloaded from the country's most popular mobile messaging service, Kakao Talk, and is relatively simple though it requires nimble hands.

It presents a screen of 49 cartoon animals, in a matrix of seven vertical columns and seven horizontal rows. The aim is to line up three identical animals by swiping the screen vertically or horizontally in one move, which results in a "combo." When the number of combos reaches a certain level, players obtain a "bomb" that destroys a vertical and horizontal row.

The developer says it restricted playing to one minute but people say that's the key element that causes them to crave the game.

"What makes the game so addictive is that I can only play it for one minute. As I can't play it as long as I want, I want to play it more," said Jin Eun-ok, a teacher at an elementary school in Gyeonggi Province.

Users are restricted to five rounds in a row and should then wait eight minutes to receive a new heart. However, they can receive hearts from other players or buy "topazs" which can be converted into hearts later.

A player's score is instantly transmitted to everyone on their Kakao Talk contact list who also plays Anipang to encourage competition among friends. Every time a round ends, people can check their rankings. The accumulated scores are automatically reset every seven days.

"I am not usually very keen on online or mobile games but this one is amazing," said 26-year-old college student Lee Jong-wook. "I am totally into to it since it's very easy to play and I can compete with my friends on Kakao Talk. I guess almost everyone around me has got into it."

Looking to the dark side

"I have to play Anipang at least twice a day otherwise I feel something is missing," said 28-year-old nutritionist Cho Hye-jin.

Things are more serious for high school student Jeong Yoon-hyeock.

"My friend told me he saw a person almost get hit by a car because he wasn't aware of the traffic lights while playing Anipang on the street," said Jeong.

The 18-year-old says the game affects his daily life saying, "I just keep thinking about it. I can't concentrate on my studies."

Psychiatrist Sohn Seok-han said experts are concerned over the addictiveness of the game. "If you play it to just have fun, it is OK. But if you play it as an escape from reality to relieve stress, it is a sign of addiction," Sohn said. "If you become restless when you are not playing the game, it is a kind of withdrawal symptom. It is more serious if it disturbs your daily life. In this case, you have to quit, not just reduce the amount of time spent playing the game."

Anipang has spread rapidly but also annoys those who don't play it.

When players run out of hearts, some impassionedly send messages to people on their KaKao Talk contact list begging for more.

"I don't play Anipang but I receive a lot of messages inviting me or begging for hearts. It really annoys me. What's worse is that I have to download the app to block the messages, even though I don't use it," said Choi Ji-na, 29, who works for a trading firm.

According to a survey of 2,860 people conducted by Dooit on Oct. 8 and 9, four out of 10 people are stressed because of these messages.

It was even worse for iPhone owners. They couldn't download Anipang as the iPhone didn't support KaKao Talk games, they only received the messages but had no way to block them.

Experts also warn that playing mobile phone games for too long can harm players' eyes.

"Your eyes produce different responses in accordance with the distance of the objects you are looking at. When you look at something close, your eyes continue to work, seeking to focus. If this lasts for a long time, it can cause or worsen near-sightedness," said Jang Gyu-jin, an ophthalmologist and director of Gangnam Eyeone Ophthalmic Clinic. "It is especially harmful for children to play mobile games, including Anipang, for a long time."

Jang added, "Even for adults, if your eyes work on focusing for long hours, the amount of blinking decreases which results in a lack of tears that provide a film coating. It can cause or aggravate dry eyes and further allergies."

Competition feature

Whether people are obsessed by the mobile game or not, many of them want to achieve higher scores than their friends.

Of the 20 million subscribers to the game, more than 6 million are elementary school students for whom Anipang scores can represent their status in the class.

Due to increasing concerns, discussions have been held on whether to include Anipang on the addictive game list that the Ministry of Gender Equality and Family will announce on Nov. 20.

A ministry official said that the ministry has no plan as yet to put Anipang on the list of games that are subject to obligatory shutdown rules applicable to addictive PC games as it's a mobile phone game.